1. Field of the Invention
The present invention relates to a roulette gaming machine configured to cause a ball to roll on a roulette board and the rolling ball to be received into one of ball receiving parts formed on a rotatable portion. More specifically, the roulette gaming machine causes the rolling ball to be received into one of the ball receiving parts while varying a period for rotating the rotatable portion at a fixed rotation speed according to a lottery result. The present invention further relates to a method for selecting a constant speed rotation period for rotating the rotatable portion.
2. Description of the Related Art
There have been conventionally various roulette gaming machines. When a player bets one or more game media on one or more desired numerals arranged on a roulette board, the roulette gaming machine causes a roulette wheel (rotatable portion) of the roulette board to rotate at a fixed rotation speed and during a fixed period. Then, a ball is launched to the roulette board and then rolls on the roulette board. If the roulette wheel slowly rotates, the rolling ball is received into one of ball receiving grooves (ball receiving parts) formed on the roulette wheel. The roulette gaming machine identifies one numeral (winning number) assigned to the ball receiving groove in which the ball is received, and then determines whether or not the one numeral is equal to one of the one or more desired numerals bet on by the player. If the one numeral is equal to one of the one or more desired numerals, the roulette gaming machine pays out game media corresponding to a dividend amount.
The conventional roulette gaming machine rotates the roulette wheel, in order to vary the winning number as randomly as possible by each roulette game to prevent skilled players from predicting the winning number surely. However, since the roulette wheel is rotated at the fixed rotation speed and during the fixed period in each roulette game, the skilled players can roughly predict a next winning number on the basis of the arrangement of the roulette wheel at the time of launching the ball.
A conventional method for solving the above-described problem is disclosed in Japanese Patent Laid-open Publication No. 2003-334275. In the conventional method, a rotation speed of a roulette wheel is varied according to a sampled random number when a certain time has elapsed since the ball is launched. It is noted that the ball is retrieved from a fixed position of the roulette wheel after the ball has been received in a ball receiving groove formed on the roulette wheel, and then launched from a fixed postion of the roulette board.
However, the conventional method needs a complicated drive control process for a motor to be employed to rotate the roulette wheel because the rotation speed of the roulette wheel is randomly varied in each roulette game. Further, in a case where a pseudo random number generating circuit is employed in the conventional method, if skilled players obtain the previous winning number, the tendency for random numbers to be generated by the pseudo random number generating circuit, and the rotation speed of the roulette wheel corresponding to each random number in each roulette game, they can roughly predict a next winning number because the arrangement of the roulette wheel is reset in each roulette game so that the ball receiving groove to which the previous winning number is assigned is located at the fixed position of the roulette wheel every time the ball is retrieved.